Liquid crystal projection device having a liquid crystal display element that includes an electroluminescent element

ABSTRACT

A liquid-crystal projection device includes an organic electroluminescent element that is sandwiched by an organic thin-film layer between an electrode layer that reflects light and a transparent electrode layer that transmits light, and a transparent liquid crystal panel that controls passage of light emitted from the surface of the organic electroluminescent element and also includes a half-mirror layer arranged on the side where light is output from the transparent electrode layer. Some of the incoming light is reflected through the transparent electrode layer to another electrode layer and the rest of the light is transmitted the distance between the half-mirror layer. The electrode layer is set to the optical distance of resonance of the light.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid-crystal projection device i.e.what is known as a projector and in particular relates to improvementsin the light source and peripheral optical system of a small-sizeliquid-crystal projection device.

2. Description of the Relate Art

As the light sources employed in conventional liquid-crystal projectiondevices, light sources using a fluorescent tube or light-guide plate orelectrical discharge-type light sources such as metal halide lamps havecome to be employed.

In particular, Japanese Patent Laid-Open number Sho.51-119243 disclosesa flat plate-shaped light source. This specification states that theflat plate-shaped light source employs electroluminescence i.e.electroluminescent elements.

However, in the case of a light source employing a fluorescent tube orlight-guide plate, it is difficult to make the diameter of thefluorescent tube etc. small. There was therefore the problem thatminiaturization of a liquid-crystal projection device was difficult,since the thickness of the light source itself could not be reducedbelow the diameter of the fluorescent tube.

Also, in the case of an electric discharge-type light source such as ametal halide lamp, the reflector of large aperture that was considerednecessary to direct the light diverging from the light source parallelto the liquid crystal panel was a factor impeding miniaturisation of theliquid-crystal projection device.

In particular in the came of a liquid-crystal projection device forcolour display, further miniaturisation of the liquid-crystal projectiondevice was difficult owing to the need to provide liquid crystal displayelements consisting of a light source as aforementioned and liquidcrystal panel for each of the primary colours constituting the colourimage.

Also, Japanese Patent Laid-Open number Sho.51-119243 does not clearlydisclose a material constituting a luminescent layer of anelectroluminescent element. When the conventional inorganicelectroluminescent material is employed as material for this luminescentlayer, light from the electroluminescent element in light of a highlydivergent character. This therefore suffered from the problem thatprojection of a bright image could not be achieved since the light couldnot be effectively directed into the aperture of the projection lens.

A further problem was that the drive voltage required for anelectroluminescent element using inorganic material is at least 100volts, which is comparatively high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid-crystalprojection device wherein, in order to solve the above problems, greaterminiaturisation than conventionally can be achieved and in which abright image can be projected with low voltage.

In more detail, a first task of the present invention is to provide aminiature liquid-crystal projection device that can be driven with lowervoltage than conventionally and whereby a brighter image thanconventionally can be projected by preventing the diminution in theamount of light produced by divergence of the light, by employing anorganic electroluminescent element having a resonator structure wherebylight of good optical emission directionality is emitted.

A second task of the present invention is to provide a miniatureliquid-crystal projection device whereby a brighter image thanconventionally can be projected by increasing the amount of light thatcan be transmitted through the polarizing plate of the liquid crystalpanel by using a polarization conversion element that can convert thecondition of polarization of the emitted light from the light source.

A third task of the present invention is to provide a miniatureliquid-crystal projection device whereby a brighter image thanconventionally can be projected, by increasing the amount of light thatcan be transmitted through the polarizing plate of the liquid crystalpanel by employing a polarisation conversion element that functions in aspecified wavelength band in projecting a colour image.

A fourth task of the present invention is to provide a miniatureliquid-crystal projection device whereby a brighter image thanconventionally can be projected by increasing the amount of light thatcan be transmitted through the aperture of a pixel and miniaturising thedevice itself by employing a miniature luminescent element comprising amicrolens array element that focuses the light on to pixel apertures ofthe liquid crystal panel.

A fifth task of the present invention is to provide a miniatureliquid-crystal projection device whereby a clear image can be projectedby raising the purity of the light that is projected and the brightnesscompared with conventionally, by increasing the amount of lightconsisting of light of only a specified wavelength by employingminiature lumuinescent elements that emit light of only a specifiedwavelength, due to optical resonance, in projection of a colour image.

A liquid-crystal projection device according to claim 1 consists in aliquid-crystal projection device having a liquid crystal display elementcomprising: an organic electroluminescent element constructed bysandwiching an organic thin-film element between an electrode layer thatreflects light and an electrode layer that transmits light; and atransparent liquid crystal panel that controls the transmission of lightemitted from a face of the organic electroluminescent element.

A liquid-crystal projection device according to claim 2 consists in aliquid-crystal projection device according to claim 1 wherein theorganic thin-film layer is constituted as a white luminescent layer thatemits white light.

A liquid-crystal projection device according to claim 3 consists in aliquid-crystal projection device according to claim 1 wherein theorganic thin-film layer is constituted by successively stacking primarycolour luminescent layers that respectively emit light of respectivewavelength regions of a plurality of primary colours necessary forcolour display.

A liquid-crystal projection device according to claim 4 consists in aliquid-crystal projection device according to claim 1 wherein theorganic electroluninescent element in constituted of a transparentelectrode layer overlying a transparent substrate, the organic thin-filmlayer overlying this transparent electrode layer and an electrode layeroverlying the organic thin-film layer and that reflects light emitted bythe organic thin-film layer.

A liquid-crystal projection device according to claim 5 consists in aliquid-crystal projection device according to claim 1 wherein theorganic electroluminescent element comprises: an electrode layer thatreflects light emitted from the organic thin-film layer; a transparentelectrode layer that sandwiches the organic thin-film layer betweenitself and this electrode layer; and a half-mirror layer provided on theoptical output side from this transparent electrode layer and thatreflects some of the incoming light through the transparent electrodelayer into the electrode layer, while transmitting the rest of thislight; and the distance between this half-mirror layer and the electrodelayer is set to an optical distance that produces resonance of the lightin question.

A liquid-crystal projection device according to claim 6 consists in aliquid-crystal projection device according to any one of claims 1 to 5wherein, between the organic electroluminescent element and thetransparent liquid crystal panel there is further provided apolarization conversion element that converts the polarization conditionof emitted light from the organic electroluimnescent element, and thetransparent liquid crystal panel is provided with a polarizing platethat transmits light of specified polarization condition, of the lightemitted after passing through the polarization conversion element.

A liquid-crystal projection device according to claim 7 consists in aliquid-crystal projection device according to claim 6 wherein thepolarization conversion element comprises: a circular polarizationselective reflection filter arranged on the organic electroluminescentelement side and that reflects one circularly polarized component ofright-handed circularly polarized light and left-handed circularlypolarized light and that transmits the other circularly polarizedcomponent, and a ¼ wavelength plate that converts circularly polarizedlight to linearly polarized light and that converts linearly polarizedlight to circularly polarized light.

A liquid-crystal projection device according to claim 8 consists in aliquid-crystal projection device according to claim 6 wherein thepolarization conversion element comprises: a linearly polarized lightselective reflection filter arranged on the transparent liquid crystalpanel side and that, of two perpendicular linearly polarized components,reflects one linearly polarized component and transmits the otherlinearly polarized component, and a ¼ wavelength plate that convertscircularly polarized light into linearly polarized light and thatconverts linearly polarized light into circularly polarized light.

A liquid-crystal projection device according to claim 9 consists in aliquid-crystal projection device according to any of claims 6 to 8wherein the polarization conversion element comprises a polarizationselective reflection filter that, for the emitted light of a specifiedwavelength region, transmits light of this specified polarisationcondition and reflects light o: other polarization conditions.

A liquid-crystal projection device according to claim 10 consists in aliquid-crystal projection device according to claim 6 wherein, betweenthe organic electroluminescent element and the transparent liquidcrystal panel, there is further provided a front-side microlens arrayelement wherein microlens elements that collect output light from theorganic electroluminescent element are arranged corresponding toindividual pixels of the transparent liquid crystal panel.

A liquid-crystal projection device according to claim 11 consists in aliquid-crystal projection device according to claim 10 wherein the focallength of the microlens elements and the distance between the front-sidemicrolens array element and this liquid crystal panel are adjusted suchthat the apertures of the individual pixels of the transparent liquidcrystal panel are arranged in the vicinity of the rear-side focal pointof the microlens elements.

A liquid-crystal projection device according to claim 12 consists in aliquid-crystal projection device according to any of claims 10 or 11wherein the transparent liquid crystal panel comprises an opticalscreening element that transmits light that is incident on the apertureof each pixel and that screens light that in incident on portions otherthan the aperture of this pixel.

A liquid-crystal projection device according to claim 13 consists in aliquid-crystal projection device according to any of claims 10 to 12,further comprising a rear-side microlens array element constituted byarranging, corresponding to individual pixels, microlens elements thatsuppress divergence of light transmitted through the pixel apertures ofthe liquid crystal panel, on the side where light is output afterpassing through the transparent liquid crystal panel.

A liquid-crystal projection device according to claim 14 consists in aliquid-crystal projection device according to claim 13 wherein the focallength of the microlens elements and the distance between this rear-sidemicrolens array element and this transparent liquid crystal panel areadjusted such that the apertures of the pixels are arranged in thevicinity of the front-side focal point of the rear-side microlenselements.

A liquid-crystal projection device according to claim 15 consists in aliquid-crystal projection device according to any of claims 10 to 14wherein, between the organic electroluminescent element and thefront-side microlens array element, there in further provided apolarization conversion element that converts the polarization conditionof light that is output from the organic electroluminescent element, andthe transparent liquid crystal panel comprises a polarizing plate thattransmits light of specified polarization condition, of the light thatis output after passing through the polarization conversion element.

A liquid-crystal projection device according to claim 16 consists in aliquid-crystal projection device according to claim 15 wherein thepolarization conversion element comprises a circular polarizationselective reflection filter arranged on the organic electroluminescentelement side and that reflects one circularly polarized component ofright-handed circularly polarized light and left-handed circularlypolarised light and that transmits the other circularly polarizedcomponent, and a ¼ wavelength plate that converts circularly polarizedlight into linearly polarized light and that converts linearly polarizedlight into circularly polarised light.

A liquid-crystal projection device according to claim 17 consists in aliquid-crystal projection device according to claim 15 wherein thepolarization conversion element comprises. a linear polarizationselective reflection filter arranged on the front-side microlens arrayelement side and that, of two perpendicular linear polarizationcomponents, reflects one linearly polarised component and transmits theother linearly polarized component, and a ¼ wavelength plate thatconverts circularly polarized light into linearly polarized light andthat converts linearly polarized light into circularly polarized light.

A liquid-crystal projection device according to claim 18 consists in aliquid-crystal projection device according to any of claims 1, 4 or 5,further provided with a projection lens that projects on to a screen animage generated by passing through the transparent liquid crystal panel.

A liquid-crystal projection device according to claim 19 consists in aliquid-crystal projection device according to claim 18 further providedwith a transparent screen whereby an image projected from the projectionlens can be observed from the opposite side of this projection lens.

A liquid-crystal projection device according to claim 20 consists in aliquid-crystal projection device according to any of claim 1 or claim 4,further provided with a plurality of liquid crystal display elementsthat control the transmission of light of respective wavelength regionsof a plurality of primary colours necessary for colour display; acombining optical system that generates a colour image by combiningimages of primary colours emitted from the plurality of liquid crystaldisplay elements; and a projection lens that projects on to a screen acolour image combined by the combining optical system.

A liquid-crystal projection device according to claim 21 consists in aliquid-crystal projection device according to claim 20 wherein theplurality of organic electroluminescent elements are provided with anoptical resonant structure.

A liquid-crystal projection device according to claim 22 consists in aliquid-crystal projection device comprising, for each primary colour,liquid crystal display elements including organic electroluminescentelements having an optical resonant structure adjusted such an to emitlight of respective wavelength regions of a plurality of primary coloursnecessary for colour display and a transparent liquid crystal panel thatcontrols the transmission of light emitted from the face of the organicelectroluminescent elements; and further comprising a combining opticalsystem that generates a colour image by combining images of each primarycolour emitted from the respective liquid crystal display elements, anda projection lens that projects on to a screen the colour image combinedby the combining optical system.

A liquid-crystal projection device according to claim 23 consists in aliquid-crystal projection device according to any of claims 20 to 22further comprising a transparent screen constituted so that an imageprojected from the projection lens can be observed from the oppositeside of this projection lens.

A liquid-crystal projection device according to claim 24 consists in aliquid-crystal projection device according to any of claims 20 to 23wherein the liquid crystal display elements further comprise, betweenthe organic electroluminescent element and the transparent liquidcrystal panel, a front-side microlens array constituted by arranging,corresponding to individual pixels of the transparent liquid crystalpanel, microlens elements that collect the light emitted from theorganic electroluminescent element.

A liquid-crystal projection device according to claim 25 consists in aliquid-crystal projection device according to claim 24 wherein theliquid crystal display elements further comprise a rear-side microlensarray element constituted by arranging, corresponding to each pixel,microlens elements that suppress divergence of light passing through thepixel apertures of the liquid crystal panel, on the output side of lightthat has passed through the transparent liquid crystal panel.

A liquid-crystal projection device according to claim 26 consists in aliquid-crystal projection device according to any of claims 24 or 25wherein the front-side microlens array element and the rear-sidemicrolens array element of the liquid crystal display elements comprisea reflection preventing film adjusted such that its reflectivity islowest for light of the wavelength region of the primary colourallocated to the liquid crystal display element in question.

A liquid-crystal projection device according to claim 27 consists in aliquid-crystal projection device according to any of claims 20 to 26wherein the liquid crystal display elements, between the organicelectroluminescent element and the front-side microlens array element,are further provided with a polarization conversion element thatconverts the polarisation condition of emitted light, from the organicelectroluminescent element, and the transparent liquid crystal panel isprovided with a polarizing plate that transmits light of specifiedpolarization condition of light that is emitted after having passedthrough the polarization conversion element.

A liquid-crystal projection device according to claim 28 consists in aliquid-crystal projection device according to claim 27 wherein thepolarization conversion element of the liquid crystal display elementscomprises a polarization selective reflection filter that transmitslight of specified polarization condition with respect to the emittedlight of a specified wavelength region and that reflects light ofpolarization condition other than this.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall layout diagram of a liquid-crystal projectiondevice according to embodiment 1 of the present invention;

FIG. 2 is a layout diagram of a liquid crystal display element 1 a(organic electroluminescent element 10 and transparent liquid crystalpanel 20) according to embodiment 1;

FIG. 3 is a layout diagram of a liquid crystal display element 1 b(organic electroluminescent element 11 and transparent liquid crystalpanel 20) according to embodiment 2;

FIG. 4 is a layout diagram of a liquid crystal display element 1 c(organic electroluminescent element 12 and transparent liquid crystalpanel 20) according to embodiment 3;

FIG. 5 is a layout diagram of a&liquid crystal display element 1 d(organic electroluimnescent element 11, polarization conversion element13 and transparent liquid crystal panel 20) according to embodiment 4;

FIG. 6 is a perspective view of a liquid crystal display element 1 d(organic electroluminescent element 11, polarization conversion element13 and transparent liquid crystal panel 20) according to embodiment 4;

FIG. 7 is a layout diagram of a liquid crystal display element 1 e(organic electroluminescent element 11, polarization conversion element14 and transparent liquid crystal panel 20) according to embodiment 5;

FIG. 8 is a perspective view of a liquid crystal display element 1 e(organic electroluminescent element 11, polarization conversion element14 and transparent liquid crystal panel 20) according to embodiment 5;

FIG. 9 in a layout diagram of a liquid crystal display element 1 f(organic electroluminescent element 12, front-side microlens arrayelement 15 and transparent liquid crystal panel 16) according toembodiment 6;

FIG. 10 is a layout diagram of a liquid crystal display element 1 g(organic electroluminescent element 12, front-side microlens arrayelement 15, transparent liquid crystal panel 16 and rear-side microlensarray element 17) according to embodiment 7;

FIG. 11 is a layout diagram of a liquid crystal display element 1 h(organic electroluminescent element 12, polarization conversion element13, front-side microlens array element 15 and transparent liquid crystalpanel 18) according to embodiment 8;

FIG. 12 is an overall layout diagram of a liquid-crystal projectiondevice according to embodiment 9;

FIG. 13 is an overall layout diagram of a transparent liquid crystaldisplay element according to embodiment 10;

FIG. 14 is an overall layout diagram of a liquid-crystal projectiondevice according to embodiment 11; and

FIG. 15 is an overall layout diagram of a liquid-crystal projectiondevice according to embodiment 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, preferred embodiments of the present invention are described withreference to the drawings.

Embodiment 1

(Layout)

A liquid-crystal projection device according to the present invention,as shown in FIG. 1, comprises a liquid crystal display element 1 a,projection lens 30 and frame 40.

Projection lens 30 in constituted such that an image emitted from liquidcrystal display element 1 a is imaged on a screen 50. Although only asingle projection lens is shown in the Figure, this could of course beconstituted by an assembly of a plurality of lenses. specifically, theprojection lens may be constructed so as to for example magnify theimage emitted from liquid crystal display element 1 a before it isformed on screen 50.

Frame 40 in constituted an a receptacle for accommodating the entireliquid-crystal projection device and is constituted such that theoptical elements are suitably arranged therein. Its material isconstituted such that it is unaffected by deformation etc. due to theheat emission by liquid crystal display element 1 a. Liquid crystaldisplay element 1 a, as shown in FIG. 2, comprises an organicelectroluminescent element 10 and transparent liquid crystal panel 20and is constructed to omit a modulated image.

Organic electroluminescent element 10 is constituted of successivelayers: transparent electrode layer 101, blue luminescent layer 102,green luminescent layer 103, red luminescent layer 104 and reflectiveelectrode layer 105 on transparent substrate 100.

Transparent substrate 100 consists of optically transparent materialsuch as glass and is constituted of material of high mechanicalstrength. Its thickness is adjusted so as not to be too thin, in orderto maintain enough mechanical strength to act as a light source, yet notto be so thick as to result in lose of optical transparency or excessiveweight. The area of this substrate is preferably slightly larger thanthe area of liquid crystal panel 20. If its area is too large, power iswasted in unused illumination and the contrast of the projected image isadversely affected by leakage of light. If the area is too small,sufficient illuminating light in not supplied to the peripheral sectionof the liquid crystal panel, producing non-uniformity of the amount oflight.

Transparent electrode layer 101 is constituted of a material havingoptical transparency such as ITO (Indium Tin oxide) and that haselectrical conductivity. Its film thickness is adjusted so that it isnot too thin for its film thickness to be kept uniform duringmanufacture yet is not so thick as to result in loss of opticaltransparency.

Blue luminescent layer 102, green luminescent layer 103 and redluminescent layer 104 are each constituted of organic thin-film layerscontaining organic molecules that emit light on application of anelectrical field. Blue luminescent layer 102 is constituted by organicmolecules that emit light in the blue-wavelength region. Greenluminescent layer 103 in constituted by organic molecules that emitlight in the groan wavelength region. Red luminescent layer 104 isconstituted by organic molecules that emit light in the red wavelengthregion.

As blue electroluminescent layer 202 that emits light of blue colour,there may be employed a laminated structure consisting of atriphenyldiamine derivative whose peak luminescence wavelength is about380 to 420 nm and a 1,2,4-triazole derivative; as green luminescencelayer 103 that emits light of green colour, there may be employedaluminium tris (8-quinolilate) whose peak luminescence wavelength inabout 520 nm; and as the rod luminescence layer 104 that emits light ofred colour, there may be employed aluminium tris (8-quinolinate) towhich has been added red luminescent chromogenic material, whose peakluminescence wavelength is about 600 nm. These materials are disclosedin science, Vol. 267 pp. 1332-1334 (1990).

Preferably the area of the luminescent layers is equal to that of thetransparent electrode layer.

Reflective electrode layer 105 is constituted comprising a metalliclayer that reflects light and has electrical conductivity.

Examples of such metals that may be given include magnesium-silveralloys etc. Its film thickness is adjusted such that the film thicknesscan be maintained uniform but does not provide excess weight. Its areain preferably the same as that of transparent electrode layer 101.

To simplify the description, the power source circuit that appliesvoltage between transparent electrode layer 101 and reflecting electrodelayer 103 is not shown in the drawing.

Transparent liquid crystal panel 20 is constituted comprising polarizingplates 201 a, 201 b, transparent substrate 203 and liquid crystal layer202. Those constructional items are the same as in a commonly knowntransparent liquid crystal panel in this Figure, in order to facilitateunderstanding, the drive circuitry provided on the transparent substrateand the display circuitry that supplies control signals to thetransparent electrode, wiring and drive circuitry are not shown.

Polarizing plates 201 a and 201 b have the same construction and areconstituted such an to transmit only light of a specified polarizationcondition of the incident light. However, the direction of polarization(direction of oscillation) of the light passing through polarizing plate201 b is arranged to be offset by a fixed angle with respect to thedirection of polarization transmitted through polarizing plate 201 a.This angle is set so as to be equal to the angle of rotation of theplane of polarization whereby liquid crystal layer 202 rotates the planeof polarization of light incident thereon when no voltage is applied toit.

For liquid crystal layer 202, a known twisted nematic liquid crystal orthe like is employed; when voltage is applied to it does not rotate theplane of polarization of incident light, but when voltage is not appliedto it, it rotates the plane of polarization of incident light.

Transparent substrate 203 is provided with a transparent electrode (notshown) on the liquid crystal layer side, and a drive circuit is providedthat is capable of driving the liquid crystal for each pixel. Theconstruction is such that optical modulation can be achieved bytransmitting or not transmitting light from organic electroluminescentelement 10 in response to change of voltage of a control signal suppliedfrom the drive circuit.

Preferably, organic electroluminescent element 10 is provided with acooling mechanism that cools the organic electroluminescent element.

(Action)

When an electrical field is applied to the electroluminescent element,this exhibits electroluminescence. When an electrical field is appliedto a material that produces electroluminescence, the electroluminescencephenomenon is produced and the electrical energy is converted intolight.

Conventionally, as electroluminescent elements, the inorganic materialsZnS, SrS, and CaS were employed. However, with these inorganicmaterials, the intensity of the light is weak, and the emitted light isnot emitted in parallel but constitutes divergent light.

In contrast, with the electroluminescent element of the presentinvention, an organic material in employed. The amount of light emitteddue to electroluminescence is large because of light emission due torecombination of electrons injected from the cathode and positive holesinjected from the anode. Luminescent layers 102 to 104 constituteluminescent elements using this organic material When voltage in appliedbetween transparent electrode layer 101 and reflective electrode layer105, an electrical field is generated corresponding to the filmthickness of the luminescent layer and the applied voltage in eachluminescent layer sandwiched by two electrode layer. The organicmolecules of each luminescent layer exhibit the electroluminescencephenomenon when they are subjected to this electrical field and generatelight in a fixed wavelength region The intensity of this light iscorrelated with the applied voltage. Each luminescent layer has anelectrical field applied to it which depends on the film thickness, gothe luminescence depends on the intensity of the electrical field. Ifthe areas of transparent electrode layer 101, luminescent layers 102 to104 and reflective electrode layer 105 are made practically equal, theintensities of the electrical fields in each portion of the luminescentlayers are practically uniform. That is, uniform light is emitted fromthe entire surface of the organic electroluminescent element. Theblue-coloured light from blue luminescent layer 102 passes directlythrough transparent electrode layer 101 and is emitted from thetransparent substrate. The green light from green luminescent layer 103passes through blue luminescent layer 102 and transparent electrode film101 to be emitted from the transparent substrate. The red light from redluminescent layer 104 passes through green luminescent layer 103, blueluminescent layer 102 and transparent electrode film 101 to be emittedfrom the transparent substrate. If the film thicknesses etc. of theluminescent layers are adjusted such that the same amount of light ofeach primary colour is emitted from the transparent substrate, whitelight is obtained by equal summation of the primary colours.

Although light is also emitted from each luminescent layer in theopposite direction to the liquid crystal panel, this light is reflectedby reflecting electrode layer 105 and returned towards liquid crystalpanel 20.

Consequently, the light that is returned from reflecting electrode layer105 is added to the light that is directly emitted from each luminescentlayer, resulting in an increased amount of light being emitted tooutside transparent substrate 100.

In particular, an organic electroluminescent element as employed in thepresent invention is well adapted as a light source for a liquid-crystalprojection device, since it has the characteristic advantages of abilityto be driven at low voltage and higher brightness than the inorganicelectroluminescent elements that were conventionally employed as a flatplate-shaped light source.

At liquid crystal panel 20, of the light from organic electroluminescentelement 10, only light having a specified plane of polarisation passesthrough polarizing plate 201 a. When a control signal is supplied to thecontrol circuit formed on transparent substrate 203, voltage is appliedbetween the transparent electrodes of the pixel in question. In a pixelthat has voltage applied between its transparent electrodes, the liquidcrystal molecules in the region of this pixel are aligned in thedirection of the electrical field. Consequently, in the case of a pixelthat has voltage applied to it, rotation of the plane of polarization isnot applied to incident light, and such light reaches polarizing plate201 b on the opposite side. However, the direction of polarization inwhich transmission is possible through polarizing plate 201 b is offsetfrom that of polarizing plate 201 a, so the incident light cannot passthrough polarizing plate 201b.

On the other hand, if control voltage is not applied to the drivecircuit, voltage is not applied between the electrodes of the pixel inquestion. In the case of a pixel to which voltage is not applied, theliquid crystal molecules in this pixel region are aligned in thehorizontal direction, so rotation of the plane of polarization isapplied to the incident light. Consequently, in the came of pixels towhich voltage is not applied, rotation of the plane of polarization isapplied to the incident light, and this therefore reaches polarizingplate 201 b on the opposite side. Polarizing plate 201 b is arrangedoffset from polarizing plate 201 a by the angle of rotation of the plansof polarization that is applied to this incident light, so the incidentlight passes through polarizing plate 201 b and reaches screen 50through projection lens 30.

In this way, display/non-display can be set up for each pixel by meansof a control signal.

The liquid crystal display element in formed of a size of for exampleabout 33 mm (1.3 inch) diagonal, and can be driven by a drive voltage ofabout 10 volts.

In order to obtain a construction in which a colour image can beprojected on to a screen, colour filters are formed in the pixels of theliquid crystal panel. By such a construction, colour can be generatedwhen white light passes through the liquid crystal panel.

As described above, with this embodiment 1, no large reflector needs tobe employed for the light source, so that the display device can beminiaturised.

Also, since the organic electroluminescent element supplies bright lightto the liquid crystal panel, a liquid-crystal projection device can beprovided in which a bright image is obtained.

Embodiment 2

Embodiment 2 of the present invention provides an organicelectroluminescent element whereby white light is obtained byluminescent layers different from those of embodiment 1.

(Construction)

A liquid-crystal projection device according to embodiment 2 has thesame construction (see FIG. 1) as embodiment 1 described above, exceptthat liquid crystal display element 1 b differs from embodiment 1 inthat, as shown in FIG. 3, it comprises an organic electroluminescentelement 11. The construction of liquid crystal panel 20 is identicalwith that of the first embodiment so a description thereof is omitted.

Organic electroluminescent element 11 is constituted by laminating atransparent electrode layer 111, white luminescent layer 112 andreflecting electrode layer 113 on to transparent substrate 110.Transparent substrate 110 is the same as transparent substrate 100 ofembodiment 1, transparent electrode layer 111 is the same an transparentelectrode layer 101 of embodiment 1, and reflecting electrode layer 113is the same as reflecting electrode layer 105 of embodiment 1,respectively, so description thereof is omitted. Depiction of the powersource circuit for applying voltage between the transparent electrodelayer and reflecting electrode layer in omitted just as in the case ofembodiment 1.

White luminescent layer 112 is an organic thin-film layer which, when anelectrical field is applied to it, emits light of a plurality ofwavelength regions, so that white light is emitted from the layer as awhole. An example that may be given of an organic thin film that emitswhite light in response to application of an electrical field is a thinfilm in which there is a molecular dispersion of a low molecularelectron transporting compound and a plurality of chromogenic materialsconstituting centres of luminescence in poly(N-vinyl carbazole) vinyl.Such a luminescent film structure is disclosed in applied PhysicsLetters vol. 67 No. 16, pp. 2281-2283 (1995).

(Action)

When voltage in applied between transparent electrode layer 111 andreflecting electrode layer 113, an electrical field is generatedcorresponding to the film thickness of this white luminescent layer andthe value of this voltage. White luminescent film 112 emitssimultaneously light of a plurality of primary colour wavelength regionsin response to the intensity of this electrical field; the light of thisplurality of wavelength regions is summed and emitted from thetransparent substrate. White light is therefore supplied to liquidcrystal panel 20.

It should be noted that, although in this embodiment, a luminescentlayer was constituted by an organic thin film emitting white light suchthat a colour image could also be projected, it would alternatively bepossible to provide as luminescent layer an organic thin film emitting asingle colour such as green, red or blue. In this came, an image of thissingle colour is generated.

In organic electroluminescent element 11, it would also be possible toprovide a cooling mechanism for cooling the organic electroluminescentelement.

As described above, with embodiment 1, a large reflector in notemployed, so the display device can be miniaturized.

Also, since a beam of bright parallel light can be supplied to theliquid crystal panel, a liquid-crystal projection device can be providedwhereby a bright image can be obtained.

Embodiment 3

Embodiment 3 of the present invention relates to an organicelectroluminescent element whose directionality in the direction normalto the light-emitting face is strong due to an optical resonantstructure and whereby light of specified wavelength is emitted.

(Construction)

A liquid-crystal projection device according to embodiment 3 has thesame construction as embodiment 1 (see FIG. 1) except for liquid crystaldisplay element 1 c. As shown in FIG. 4, liquid crystal display element1 c comprises an organic electroluminescent element 12 and a transparentliquid crystal panel 20. Liquid crystal panel 20 is identical with thatof embodiment 1, so further description in omitted.

Organic electroluminescent element 12 in constituted by successivelayers consisting of transparent substrate 120, a dielectric mirrorlayer 121, a spacing adjustment layer 122, a transparent electrode layer123, a positive hole transport layer 124, a luminescent layer 125, andreflecting electrode layer 126.

Transparent substrate 120 is the same an transparent substrate 100 ofembodiment 1, transparent electrode layer 123 is the same as transparentelectrode layer 101 of embodiment 1, and reflecting electrode layer 126is the same as reflecting electrode layer 105 of embodiment 1,respectively, so further description is omitted. Just an in embodiment1, depiction of the power source circuitry for applying voltage betweenthe transparent electrode layer and reflecting electrode layer isomitted.

Dielectric mirror layer 121 is provided with a dielectric multi-layerfilm and is constituted to function as a half mirror.

Specifically, thanks to this multi-layer film structure, dielectricmirror layer 121 is constructed so as to transmit part of the incidentlight and to reflect the remainder. As such a dielectric, astacked-layer construction of for example Tio₂ (titanium oxide) and SiO₂(silicon oxide) may be employed.

Regarding the film thickness, the number of stacked layers of dielectricmulti-layer film and the film thickness of the dielectric films aredetermined in correspondence with the resonance wavelength such thatabout half of the incident light is reflected and the rest istransmitted. An optical resonator in constituted by the dielectricmulti-layer film and reflecting electrode. Spacing adjustment layer 122is provided in order to adjust the 15 distance between dielectric mirrorlayer 121 and reflecting electrode layer 126, and is constituted of atransparent dielectric film such an SiO₂.

Also, if the film thickness of positive hole transport layer 124 andluminescent layer 125 are not such as to satisfy the followingconditions, this spacing adjustment layer 122 could be omitted. Positivehole transport layer 124 is a layer for transporting positive holes toluminescent layer 125 when positive holes are injected from the anodeconstituted by transparent electrode layer 101, and consists for exampleof a triphenyldiamine derivatives The gap constituted by spacingadjustment layer 122 is adjusted such that the optical distance ofdielectric mirror layer 12i and reflecting electrode layer 126 satisfiesthe condition of being an integral multiple of half wavelengths of thepeak wavelength of the light emitted from this organ electroluminescentelement.

In order to obtain the desired colour of emitted light, the organicelectroluminescent element is constructed by adjusting the material ofluminescent layer 125 and the resonator length of the resonatorstructure. For example, to constitute a luminescent layer 125 that emitslight in the green region, a luminescent layer is constructed using amaterial such as aluminium tris (8-quinolilate) In this case, an organicelectroluminescent element that emits light with a narrow-bandluminescence spectrum in the green region, providing a peak wave lengthof 540 nm with a half-value width of 60 nm can be constructed.

To construct a luminescent layer 125 that emits light in the red region,a luminescent layer may be constituted using a material in which a redfluorescence chromogenic material in dispersed in aluminum trio(8-quinolilate) and/or a europium (Eu) complex. In this case, a peakwavelength of about 610 nm may be obtained. A luminescent layercontaining a europium complex is disclosed in Japanese Journal ofApplied Physics Vol. 34 pp. 1883-1887.

To construct a luminescent layer 125 that emits light in the blueregion, a luminescent layer may be constituted using a material such asa distyrile biphenyl derivative. A technique of constituting aluminescent layer of a distyrile biphenyl derivative is disclosed in OyoButsuri Vol. 62, (no. 10), pp. 1016-1018 (1993).

Although in this embodiment a stacked-layer construction of luminescentlayers and positive hole transport layer was employed, it wouldalternatively be possible to employ a stacked-layer construction ofluminescent layers, positive hole transport layer and electron transportlayer.

Also, it in desirable to provide a cooling mechanism in organicelectroluminescent element 12 in order to cool the organicelectroluminescent element.

Furthermore, separate provision of a filter that transmits light of therequired wavelength and absorbs light of unrequired wavelengths on theemission side of light of the organic electroluminescent element 12 isdesirable.

(Action)

An organic electroluminescent element according to the present inventionemits light of specified wavelength by utilizing the optical resonanceeffect.

When a prescribed voltage (for example about 10 volt) in applied betweentransparent electrode layer 122 and reflecting electrode layer 126, anelectric field is generated between the two electrode layers, and lightis emitted from luminescent layer 125 in accordance with the intensityof this electric field. Some of this light passes through dielectricmirror layer 121 while the remainder is reflected. The reflected lightin again reflected by reflecting electrode layer 126 and reachesdielectric mirror layer 121. At dielectric mirror layer 121, again someof the light is transmitted while the rest is reflected, so as thereflection of the light between the reflecting surface of dielectricmirror layer 121 and reflecting electrode layer 126 is repeated, andwhat is known an optical resonance is generated.

The wavelength of the resonating light depends on the optical distancebetween dielectric mirror layer 121 and reflecting electrode layer 126.if this optical distance satisfies the condition of being an integralmultiple of the half wavelength of the emitted light, optical resonanceis generated.

Consequently, since, of the wavelengths contained in the light that isemitted from luminescent layer 125, light that does not satisfy thiscondition is suppressed, only light that satisfies the aforementionedcondition passes through dielectric mirror layer 121 and is emitted.Consequently, the wavelength band of the luminescence spectrum isnarrower than in the embodiment described above. That is, luminescenceoccurs with a specific colour. This resonance effect is disclosed indetail in Applied Physics Letters, Vol. 68, (No. 19), p. 1 to 3 (1996),Applied Physics Letters, Vol 65, (No. 15), p. 1868-1870 (1994) and inElectronic Information Communication Society Technical Research Reports(Denshi Joho Tsushin Gakkai Gijutsu Xenkyu Hokoku) OME 94-79 etc. Also,technical information concerning raising the directionality in thefront-side direction of an organic electroluminescent element iscontained in articles in Applied Physics Letters Vol. 63, (No. 15), p.2023-2034 etc.

With embodiment 3 as described above, an organic electroluminescentelement that has strong directionality of the emitted light in thenormal direction (front-side direction) of the organicelectroluminescent element and whereby light emission can be restrictedto a specified wavelength can be provided without using a bulky lightsource such as a reflector; a liquid-crystal projection device cantherefore be made of smaller size than conventionally.

Also, since the organic electroluminescent element in brighter than aconventional electroluminescent element, by manufacturing such elementsfor the respective primary colours for colour display, and combiningtheir images, a bright colour image can be displayed.

Embodiment 4

Embodiment 4 of the present invention relates to an organicelectroluminescent element employing & polarization conversion element.

(Construction)

A liquid-crystal projection device according to embodiment 4 haspractically the same construction as embodiment 1 described above (seeFIG. 1) apart from liquid crystal display element 1 d. As shown in FIG.5 and FIG. 6, liquid crystal display element Id comprises an organicelectroluminescent element 11, polarization conversion element 13 andtransparent liquid crystal panel 20. Since organic electroluminescentelement 11 is of the same construction as in the case of embodiment 2and transparent liquid crystal panel 20 in of the same construction asin embodiment 1, further description thereof is omitted.

It should be noted that organic electroluminescent element 11 of thisembodiment could be directly substituted by organic electroluminescentelement 10 described in embodiment 1 or organic electroluminescentelement 12 described in embodiment 3.

Also, in these Figures; in order to make the Figures easier to view,organic electroluminescent element 11, polarization conversion 20element 13 and transparent liquid crystal panel 20 are shown an beingseparated by a large spatial distance. In fact, in order to supply lightfrom electroluminescent element 11 to the liquid crystal panel in anefficient manner, these may be arranged adjacent each other withoutmutually intervening space or the gap between these elements may befilled with transparent material.

Polarization conversion element 13 may be constructed comprising aquarter wavelength film 131 and cholesteric liquid crystal layer 132.

Cholesteric liquid crystal layer 132 in constituted of cholesteric phaseliquid crystal material; when light is directed on to this, circularlypolarized light of a direction of rotation coincident with the helicaldirection of the cholesteric structure is reflected, whereas circularlypolarized light rotating in the opposite direction to this helicaldirection is transmitted. For convenience in description, circularlypolarized light of direction of rotation capable of being transmitted bycholesteric liquid crystal layer 132 is taken as right-handed circularlypolarized light L+, while circularly polarized light of direction suchas is reflected without being transmitted is taken as left-handedcircularly polarized light L−.

Quarter-wavelength film 131 has an optic axis 133 parallel to the planeof the drawing and is constituted with optical anisotropy such that itconverts circularly polarized light to linearly polarized light. Thisoptic axis 133 is arranged to be parallel to one side of the rectangularexternal shape of polarization conversion element 13.

(Action)

The light emitted from organic electroluminescent element 11 is naturallight whose direction of oscillation (polarization direction) is randomand includes a clockwise polarized light component L+ and ananticlockwise polarized light component L−. Circularly polarizedcomponents in these two directions are incident on to cholesteric liquidcrystal layer 132. of the circularly polarized light that is incident oncholesteric liquid crystal layer 132, right-handed circularly polarizedcomponent L+ can be transmitted through this liquid crystal layer 132.Quarter-wavelength film 131 converts incident right-handed circularlypolarized light into linearly polarized light 134 a oscillating in thedirection that makes an angle of 45° with respect to one side of theouter rectangular shape of polarization conversion element 13 beforeoutputting it.

In contrast, the left-handed circularly polarized component L− isreflected by this liquid crystal layer and again returned to organicelectroluminescent element 11. Left-handed circularly polarizedcomponent L− that is returned to organic electroluminescent element 11is reflected by reflecting electrode layer 113. When the circularlypolarized light is reflected at the metal surface, the direction ofrotation of left-handed circularly polarized component (L−) in inverted,converting it to right-handed circularly polarized component L+.light-handed circularly polarized component L+ is again input topolarisation conversion element 13. Since the direction of rotation ofthe circularly polarized component is now inverted to constitutecircularly polarized component L+, this is transmitted throughcholesteric liquid crystal layer 132 and is emitted toquarter-wavelength film 131.

At quarter-wavelength film 131, the right-handed circularly polarizedlight that is transmitted through cholosteric liquid crystal layer 132is converted to linearly polarized light 134 b that oscillates in adirection making an angle of 45° with respect to one side of theexternal rectangular shape of polarization conversion element 13, and istherefore emitted by transparent liquid crystal panel 20. In short, eventhrough the light that is emitted from organic electroluminescentelement 11 has a random polarization condition, it can be finallysupplied to the transparent liquid crystal panel as linearly polarizedlight with the direction of polarization aligned.

If the direction of polarization of linearly polarized light 134 a and134 b that is supplied to transparent liquid crystal panel 20 coincideswith the direction of polarization in which polarizing plate 201 a cantransmit, the quantity of light that can be employed for opticalmodulation in the transparent liquid crystal panel can be made large.

It should be noted that the principles of a polarization conversionelement constructed of a quarter-wavelength film 131 and cholestericliquid crystal layer 132 are disclosed in Reference: Proceedings of the15the International Display Research Conference, 1995, p. 735-738,Japanese Journal of Applied Physics, Vol. 29, (No. 4), April 1990, p. L634-637 or Japanese Journal of Applied Physics, Vol. 29, (No. 10),October, 1990, p.1974-1984.

Since, with embodiment 4 am described above, of the light which isemitted from the organic electroluminescent element, all of the lightthat would otherwise fail to pass through the polarizing plate and beabsorbed i.e. more than half of the light can be supplied for opticalmodulation by the transparent liquid crystal panel, so, ideally, animage that is twice as bright as conventionally can be projected on tothe screen.

Embodiment 5

Embodiment 5 of the present invention relates to a modified example ofthe polarization conversion element of embodiment 4.

(Construction)

The liquid-crystal projection device of embodiment 5 is the same asembodiment 4 apart from liquid crystal display element 1 e. As shown inFIG. 7 and FIG. 8, liquid crystal display element 1 e comprises organicelectroluminescent element 11, polarization conversion element 14 andtransparent liquid crystal panel 20.

Organic electroluminescent element 11 and transparent liquid crystalpanel 20 have the same construction as in embodiment 4, so furtherdescription thereof is omitted.

Polarization conversion element 14 comprises a micro polarization beamsplitter array 141 and quarter-wavelength film 142. Micro polarizationbeam splitter array 141 is constructed so an to form a plurality ofmicroprisms 143 by mutual meshing together of two members withzigzag-shaped surface irregularities. Microprisms 143 are formed suchthat their boundary lines form a roof shape of 45° angle with respect tothe plans of the drawing. The boundary faces of microprisms 143 areformed by means of a dielectric multi-layer film structure or the like,so as to transmit light of specified polarization condition and toreflect light of polarization condition other than this. In thisembodiment, for convenience in description, it will be assumed that theytransmit linearly polarized light of one polarization direction (ppolarization) and reflect linearly polarized light (s polarization) inthe direction of polarization orthogonal to this.

Quarter-wavelength film 142 has the same construction anquarter-wavelength film 131 of embodiment 4 and has an optic axis 144parallel to the plane of the Figure.

It should be noted that, in place of organic electroluminescent element11 of this embodiment, there could be substituted organicelectroluminescent element 10 as described in embodiment 1 or organicelectroluminescent element 12 as described in embodiment 3.

In particular, the polarization separation characteristic of micropolarization beam splitter array 141 constituting polarizationconversion element 14 of this embodiment shows considerable dependenceon the angle of incidence of the incident light. It is thereforedesirable to employ polarization conversion element 12 of embodiment 3having an optical resonance construction in order to raise thedirectionality of the light incident on to micro polarization beamsplitter array 141.

(Action)

As described in embodiment 4, the light that is emitted from organicelectroluminescent element 11 is natural light having a random directionof oscillation and including a right-handed circularly polarizedcomponent L+ and an anticlockwise circular polarized component L−. Ofthe light that in emitted from organic electroluninescent element 11,the right-handed circularly polarized component L+ is converted to ppolarized light by quarter-wavelength film 142 and is input to micropolarization beam splitter array 14. Since the p polarized light iscapable of being transmitted by micro prisms 143, it in supplied totransparent liquid crystal panel 20 as linearly polarized light 145 a inthis unaltered polarization condition.

In contrast, of the light that is emitted from organicelectroluminescent element 11, the left-handed circularly polarizedcomponent L− is converted to B polarized light by quarter-wavelengthfilm 142 and is input to micro polarization beam splitter array 14. Thes polarized light is reflected by microprisms 143. The boundary faces ofthe microprisms 143 are inclined at 45° with respect to the direction ofincidence of the light, so the initial reflection changes the directionof the a polarized light to a direction at right angles to the directionof incidence and the second reflection changes its direction to theopposite direction to the direction of incidence. This reflected apolarized light in again converted to left-handed circularly polarizedlight L− by quarter-wavelength film 142, and is returned to organicelectroluminescent element 11.

In organic electroluminescent element 11, this returned left-handedcircularly polarized light L− is reflected by reflecting electrode layer113. When left-handed circularly polarized light L− is reflected, it isconverted into right-handed circularly polarized light L−. Thisclockwise polarized light L− is converted into p polarized light byquarter-wavelength film 142, so it now passes through microprisms 143and is supplied to transparent liquid crystal panel 20 as linearlypolarized light 145 b oscillating in the same direction as linearlypolarized light 145 a.

In short, even though the light that is emitted from organicelectroluminescent element 11 has a random polarization condition, it infinally supplied to the transparent liquid crystal panel an linearlypolarized light all having the same direction of polarization.

The principles of a micro polarization beam splitter array are disclosedin society for Information Display International Symposium Digest ofTechnical Papers, Vol. XXXXT, 1992, pp. 427-429.

As described above, with embodiment 5, of the light that is emitted fromthe organic electroluminescent element, all of the light can be suppliedfor optical modulation by the transparent liquid crystal panel, whereasconventionally more than half of the light could not pass through theconventional polarizing plate and was absorbed; ideally, therefore, animage twice as bright as conventionally can be projected on to thescreen.

Embodiment 6

Embodiment 6 of the present invention relates to a liquid crystaldisplay device using a front-side microlens array element.

(Construction)

A liquid-crystal projection device according to this embodiment 6 hasthe same construction as embodiment 1 described above with the exceptionof liquid crystal display element if. As shown in FIG. 9, liquid crystaldisplay element 1 f comprises an organic electroluminescent element 12,front-side microlens array element 15, and transparent liquid crystalpanel 16. organic electroluminescent element 12 has the same opticalresonance construction an already described with reference to embodiment3, so further description thereof is omitted.

Front-side microlens array element 15 is constructed by providing aplurality of microlens elements 151 arranged corresponding to the pixelsof transparent liquid crystal panel 16. For example, transparent liquidcrystal panel 16 comprises 640 (horizontal) ×480 (vertical) pixels,front-side microlens array element 15 also comprises 640×480 microlenselements 11. Front-side microlens array 13 is constituted by a method ofmanufacture such as plastic injection moulding or glass-press forming,using a mould formed with microlens elements 151 of lens surface shape.Also, the individual microlens elements 151 could be formed asdiffraction lenses.

The lens surface shape of the individual microlens elements 151 isformed such as to provide a fixed focal length (for example 2.5 mm) withrespect to the wavelength of the light emitted from organicelectroluminescent element 12. This focal length is the rear-side focallength of microlens elements 151. The distance between front-sidemicrolens array element 15 and transparent liquid crystal panel 16 isadjusted such that this focal length is equal to the distance from theprincipal point of microlens elements 151 to aperture 163 of a pixel oftransparent liquid crystal panel 16. A reflection-preventing film 152 isformed on both the light input face and light output face of microlenselements 131. This reflection preventing film 152 is preferably designedsuch that reflectivity is lowest for light of the wavelength emitted byorganic electroluminescent element 12.

Transparent liquid crystal panel 16 is constructed such that liquidcrystal layers 162 are sandwiched on either side by transparentsubstrate 161. On one face of transparent substrate 161, there inprovided an optical screening pattern 164 provided with apertures 163for each pixel. In order to simplify the drawing, the drive circuitryand transparent electrodes etc. provided on the polarization plate(corresponding to polarization plates 201 a, 201 b of transparent liquidcrystal panel 20 of FIG. 2) are omitted in this Figure, and the numberof pixels shown is reduced. The composition of transparent substrate 161and the liquid crystal material of liquid crystal layer 162 are the sameas in embodiment 1, so further description thereof is omitted.

Optical screening pattern 164 is constituted of a material such ascarbon that shows optical absorption and can be formed by printing orpasting in substrate form. Thus, of the light that is emitted totransparent liquid crystal panel 16, only light that is directed on toapertures 163 is emitted at the projection lens side, light that isdirected on to optical screening pattern 164 being cut off. It should benoted that optical screening pattern 164 is not essential if the lightemitted from organic electroluminescent element 12 can be completelyconcentrated on to apertures 163 of transparent liquid crystal panel 16by front-side microlens array element 15.

(Action)

When a fixed DC voltage (for example about 10 volts) is applied betweentransparent electrode layer 122 and reflecting electrode layer 126 oforganic electroluminescent element 12, light is emitted from luminescentlayer 125. Then, as described with reference to embodiment 3, light ofspecified wavelength determined by the distance between dielectricmirror 121 and reflecting electrode layer 126 is emitted from organicelectroluminescent element 12. The wavelength band of the emissionspectrum of this emitted light is narrow. microlens elements 151 aredesigned such that the focal point in aperture 163 of transparent liquidcrystal panel 16 is focused for light of this specified wavelength. Incontrast, for light of other than the specified wavelength, the degreeof refraction produced by the lens is different, so such light isbrought to a focus either upstream or downstream in the optic axisdirection with respect to aperture 163, producing a large ring of lightat aperture 163.

Consequently, light of the specified wavelength passes through aperture163 and is emitted at the projection lens side, but most of light ofwavelengths other than this is either absorbed or reflected by opticalscreening pattern 164 and so is not emitted to the projection lens.

The greater the degree of parallelism of the light that is input tomicrolens array element 15, the smaller is the focal spot produced bymicrolens elements 151, so the amount of light that can pass throughpixel apertures 163 is increased.

On the other hand, if the parallelism of the light that is input tomicrolens array 15 is lower i.e. it is more divergent, the light cannotbe sufficiently focused by microlens elements 151 and so the focal spotbecomes larger than pixel aperture 163, resulting in light beingabsorbed or reflected by optical screening pattern 164. The amount oflight that can be transmitted through aperture 163 is thereby lowered,making the image that is projected on to the screen darker.

Consequently, use of an organic electroluminescent element having anoptical resonance construction whereby the directionality of emittedlight can be raised is particularly desirable in the present embodimentemploying a microlens array element, in order to increase the amount oflight that can pass through the pixels of the liquid crystal panel.

It should be noted that, if a microlens array element 15 were not used,light absorbed or reflected by optical screening pattern 164 would beunable to pass through the liquid crystal panel, so the image projectedon to the screen would be dark.

As described above, with this embodiment 6, since an organicelectroluminescent element having a resonance construction of excellentdirectionality is employed for the emitted light, this can be focused onto the pixel apertures of the liquid crystal panel by the microlensarray element, enabling the amount of light that can be transmittedthrough the pixel apertures to be increased; colour display of highbrightness and colour purity can thus be achieved with theliquid-crystal projection device for colour display.

Embodiment 7

Embodiment 7 of the present invention relates to a liquid crystaldisplay device further employing a rear-side microlens array element.

(Construction)

A liquid-crystal projection device according to the seventh embodimenthas the same construction a embodiment 6 described above apart fromliquid crystal display element 1 g. An shown in FIG. 10, liquid crystaldisplay element 1 g is constituted comprising an organicelectroluminescent element 12, front-side microlens array element 15,transparent liquid crystal panel 16 and rear-side microlens array 17.organic electroluminescent element 12, front-side microlens arrayelement 15 and transparent liquid crystal panel 16 are the same asdescribed in embodiment 6, so further description thereof is omitted.

Rear-side microlens array element 17 is constituted comprising aplurality of microlens elements 171 arranged corresponding to the pixelsof transparent liquid crystal panel 16. For example, if transparentliquid crystal panel 16 is constituted of 640 (horizontal)×480(vertical) pixels, rear-side microlens element 17. is likewiseconstituted of 640×480 microlens elements 171.

Rear-side microlens array element 17 is constructed. by a method ofmanufacture such as plastic injection moulding or glass press forming,using a mould formed with lens surface shapes of microlens elements 171.Alternatively, microlens elements 171 could be constructed bydiffraction lenses. The lens surface shape of the individual microlenselements 171 is formed such as to provide a fixed focal length (forexample 2.5 mm) for light of the specific wavelength emitted by organicelectroluminescent element 12.

This focal length is the front focal length of microlens element 171.The distance between transparent liquid crystal panel 16 and rear-sidemicrolens array element 17 is adjusted such that this focal length isequal to the distance from pixel elements 163 of transparent liquidcrystal panel 16 to the principal point of microlens element 171. Forexample, if the focal length on the rear side of front microlens arrayelement 15 and the focal length on the front side of rear microlenselement 17 are met to the same distance, the distance between frontmicrolens array element 15 and pixel aperture 163 and the distancebetween rear microlens array element 17 and pixel aperture 163 arearranged to be the same.

A reflection-preventing film 172 in formed on both the optical inputface and optical output face of rear microlens element 171.

Preferably reflection-preventing film 172 is designed much as to providelowest reflectivity in respect of the wavelength of the light that isadmitted by organic electroluminescent element 12.

(Action)

As described above in embodiment 6, light that is input to transparentliquid crystal panel 16 is brought to a focal point at pixel aperture163 and then constitutes divergent light 165. Microlens elements 171 ofrear-side microlens array element 17 are designed such that theirfront-side focal length is equal to the distance of aperture 163.Divergent light 165 is therefore again converted into parallel light bythis microlens array element 17.

Since, as described above, with this seventh embodiment, the rear-sidemicrolens array element suppresses divergence of the light passingthrough liquid crystal panel 16, a liquid-crystal projection device canbe provided that is capable of projecting an even brighter image.

Embodiment 8

The eighth embodiment of the present invention relates to a liquidcrystal display device employing both a polarization conversion elementand a microlens array element.

(Construction)

A liquid-crystal projection device according to embodiment 8 has thesame construction as embodiment 1 described above apart from liquidcrystal display element 1 h. As shown in FIG. 11, liquid crystal displayelement 1 h comprises an organic electroluminescent element 12,polarization conversion element 13, front-side microlens array element15 and transparent liquid crystal panel 18.

Organic electroluminescent element 12 has the same optical resonantconstruction as that described in embodiment 3; polarization conversionelement 13 is the same an described in embodiment 4; and front-sidemicrolens array element 15 is of the same construction as described inembodiment 6; further description thereof in therefore omitted.

Transparent liquid crystal panel 18 is constituted comprising twotransparent substrates 181, liquid crystal layer 182 and polarizingplates 185 a and 185 b. on one of the liquid crystal layer sides oftransparent substrate 101, there is provided an aperture 183 for eachpixel and a screening pattern 184 in provided around its periphery.Since transparent substrate 181, aperture 183 and optical screeningpattern 184 ore respectively the same as transparent substrate 161,aperture 163 and screening pattern 184 of transparent liquid crystalpanel 16 of embodiment 6, description thereof is omitted. In order tofacilitate understanding of the drawing, just an in the case ofembodiment 1, the drive circuit provided on the transparent substrateand the display circuit etc. for supplying control signals to thetransparent electrodes, wiring and drive circuit are not shown.

As liquid crystal layer 182, a known twisted nematic liquid crystal orthe like is employed; this is arranged such that in the condition inwhich voltage is applied it does not rotate the plane of polarization ofthe incident light but in the condition when voltage is not applied itdoes rotate the plane of polarization of incident light.

Polarizing plates 185 a and 185 b have the same construction and arearranged such as to transmit only light of a specified polarizationcondition of the incident light. However, the direction of polarizationof light transmitted by polarizing plate 185 b is arranged to be offsetby a certain angle with respect to the direction of polarization oftransmission by polarizing plate 185 a.

This angle is met to be equal to the angle of rotation of the plane ofpolarization that is produced when the plane of polarization of incominglight is rotated when no voltage is applied to liquid crystal layer 182.

Also, the direction of polarization of linearly polarized light emittedfrom polarizing conversion element 13 is arranged to coincide with thedirection of polarization capable of being transmitted by polarizingplate 185 a. Furthermore, the distance between the principal point ofmicrolens element 151 of front-side microlens array element 15 andaperture 183 of transparent liquid crystal panel 18 is set to be equalto the rear-side focal length of microlens element 151.

For convenience in description, it is assumed that circularly polarizedlight of the direction of rotation that is capable of being transmittedby cholesteric liquid crystal layer 132 is right-handed circularlypolarized light L+, while the circular polarization of direction ofrotation that is reflected without being transmitted in left-handedcircularly polarized light L−.

(Action)

The wavelength region of light that is emitted from organicelectroluminescent element 12 is restricted by the optical resonancestructure (see embodiment 3). However, the direction of oscillation ofthe light is random and includes both a right-handed circularlypolarized component L+ and an left-handed circularly polarized componentL−. Circularly polarized components in both these directions are inputto cholesteric liquid crystal layer 132. Since, of the circularlypolarized components that are input to cholesteric liquid crystal layer132, right-handed circularly polarized component L+ can be transmittedthrough this liquid crystal layer 132, it is input to quarter-wavelengthfilm 131. Quarter-wavelength film 131 converts right-handed circularlypolarized incoming light into linearly polarised light 134 a oscillatingin a direction that makes an angle of 45° with respect to one side ofthe external rectangular shape of polarization conversion element 13. onthe other hand, left-handed circularly polarized component L− isreflected by this liquid crystal layer and is returned once more toorganic electroluimnescent element 12. Left-handed circularly polarizedcomponent L− that has returned to organic electroluminescent element 12reaches reflecting electrode layer 126, where it is reflected. When thecircularly polarized light in reflected, left-handed circularlypolarized light component L− has its direction of rotation reversed andbecomes right-handed circularly polarized light component L+.

Right-handed circularly polarized component L+ is again input topolarization conversion element 13. This time, since the circularlypolarized component has been reversed in direction of rotation, becomingright-handed circularly polarized component L+, it is able to passthrough cholesteric liquid crystal layer 132 and is emitted toquarter-wavelength film 131.

Quarter-wavelength film 131 converts the right-handed circularlypolarized light that has passed through cholesteric liquid crystal layer132 to linearly polarized light 134 b making an angle of 45° withrespect to one side of the rectangular external shape of thepolarization conversion element and oscillating in the same direction asthe direction of oscillation of linearly polarized light 134 a; thislinearly polarized light 134 b is then output to transparent liquidcrystal panel 18.

In short, whatever the polarization condition of the light that isemitted from organic electroluminescent element 12, the light that issupplied to transparent liquid crystal panel 18 is aligned in directionof oscillation and close to parallel.

Since, in this embodiment, an organic electroluminescent element havinga resonator structure is employed as light source, the wavelength bandof the emission spectrum of the emitted light is narrowly defined. Thepolarization selective reflection function of the polarizationconversion element and the optical characteristics of the microlensarray element can therefore be optimized for this specific wavelengthregion only.

The wavelength dependence of the polarization selective reflectionfunction of the polarization conversion element is determined, in thecase of the polarization conversion element in embodiment 4, by thehelical period of cholesteric liquid crystal layer 132 and, in the caseof the polarization conversion element in embodiment 5, is determined bythe layer-stacking period of the dielectric multi-layer film.

In attempting to confer a polarization selective reflection function ina wavelength region including red, green and blue, the need thereforearises to superimpose in multiple stages helical periodical structuresor stacked-layer periodical structures corresponding to each primarycolour in each of the polarization conversion elements. However, theconstruction of the polarization conversion element is straightforwardin that, when constructing polarization conversion elements functioningonly in respective specified wavelength regions such as red, green orblue, it suffices to provide a helical periodical structure orstacked-layer periodical structure corresponding just to that wavelengthregion.

Microlens elements 151 constituting front-side microlens array element15 focus light from polarization conversion element 13 on to apertures183 or transparent liquid crystal panel 18.

The direction of polarization of linearly polarized light 134 a and 134b supplied to transparent liquid crystal panel 20 coincides with thedirection of polarization that is capable of passing through polarizingplate 185 a. This linearly polarized light 134 a and 134 b thereforepasses through polarizing plate 185 a and is focused on to pixelaperture 183.

When no electric field is applied to liquid crystal layer 192, liquidcrystal layer 182 rotates the plane of polarization of incident light bya fixed angle. And when an electric field is applied to liquid crystallayer 182, the liquid crystal molecules are aligned in the direction ofthe electrical field and no polarization plane rotation is applied toincident light.

Consequently, in the case of pixels to which voltage is not applied, theplane of the incident light is rotated, allowing the light to passthrough polarizing plate 185 b and to be output at the projection lensside. In contrast, in the case of pixels to which voltage is applied, norotation in applied to the plane of polarization of the incoming lightwhich therefore cannot pass through polarizing plate 185 b and isabsorbed or reflected.

As described above, with this embodiment 8, thanks to the organicelectroluminescent element, intense light of a specified wavelength andexcellent directionality is extracted, the direction of polarization isaligned by means of the polarization conversion element, and the amountof light that can pass through the pixel apertures is increased by themicrolens array element; a liquid-crystal projection device whereby abright projected image can be obtained can therefore be provided.

Embodiment 9

Embodiment 9 of the present invention relates to a liquid-crystalprojection device of a mode wherein an image projected on to a screencan be observed from the rear.

(Construction)

As shown in FIG. 12, a liquid-crystal projection device according to thepresent invention comprises a liquid crystal display element 1,projection lens 31, frame 41 and screen 51.

The liquid crystal display elements 1 a, 1 b, 1 c, 1 d, 1 e, 1 f, 1 gand 1 h of embodiments 1 to 8 can be applied to liquid crystal displayelement 1. In other words, organic electroluminescent element 10 andtransparent liquid crystal panel 20 in this Figure are shown by way ofexample and the optical elements of the foregoing embodiments could beapplied in place of these.

Projection lens 31 is constructed such that an image that is output fromliquid crystal display element 1 is focused on screen 51. Only oneprojection lens is shown in the Figure, but this could of course beconstituted by an assembly of a plurality of lenses.

Specifically, this is constituted such that an image emitted from liquidcrystal display element 1 is brought to a focus on screen 51 aftermagnification etc.

However, if a liquid crystal display element 1 f according to embodiment6 or a liquid crystal display element 1 h according to embodiment 8 isemployed, the output light is divergent light. Projection lens 31 istherefore adjusted such that this divergent light in brought to a focuson screen 51.

Also, in this embodiment, the image is observed from the rear side ofthe screen, so the image that is projected on to screen 51 must beinverted compared with embodiment 1. Projection lens 31 is thereforeconstructed so as to invert the projection image before displaying it.

Frame 41 is constructed such that liquid crystal display element 1,projection lens 31 and screen 51 can be arranged at suitable distances.

In order to enable the image that is projected on to the screen to beobserved from behind the screen, screen 51 is constructed of for examplea semi-transparent film or a resin plate having a Fresnel lens.

(Action)

The image that is output from liquid crystal display element 1 isfocused on to screen 51. The observer observes the image displayed onscreen 51 from the rear.

For example, if the diagonal size of liquid crystal display element 1 isassumed to be 33 mm (1.3 inches) and the magnification factor ofprojection lens 31 is assumed to be about 12 times, the image displayedon screen 51 will be of diagonal size 400 mm (15.6 inches). With thisembodiment 9 as described above, an image in projected on to atransparent screen using a liquid crystal display element according tothe present invention, so a projected image can be provided that isbrighter than with a device using a conventional electroluminescentelement.

Embodiment 10

Embodiment 10 of the present invention provides a liquid-crystalprojection device for colour display use.

(Construction)

As shown in FIG. 13, a liquid-crystal projection device according tothis embodiment comprises a red liquid crystal display element 1R, agreen liquid crystal display element 1G, a blue liquid crystal displayelement 1 a, a red wavelength film 70R, a green wavelength film 70G, ablue wavelength film 70B, a dichroic prism 60, a projection lens 32, aframe 42 and screen 51. Hereinbelow, of the three primary coloursemployed in this embodiment, optical elements relating to red colour aredenoted by affixing the suffix R, optical elements relating to greencolour by the suffix G, and optical element relating to blue colour bythe suffix 9, respectively. As liquid crystal display elements 1R, 1Gand 1B, there are applied liquid crystal display elements respectivelyequipped with an organic electroluminescent element that emits light ofred colour, an organic electroluminescent element that emits light ofgreen colour or an organic electroluminescent element that emits lightof blue colour, as light source.

However, the degree of refraction by projection lens 32 must be varied,since the emitted light shows some degree of divergence when 1 f and 1 hincluding a front-side microlens array element (reference numeral 15 inFIG. 9) are applied to a liquid crystal display element.

Also, a liquid crystal display element is employed in which thewavelength of the emitted light is adjusted when 1 c, 1 f, 1 g and 1 hincluding organic electroluminescent elements (reference numeral 12 inFIG. 4 and FIG. 9 to FIG. 11) having an optical resonance structure areapplied in the liquid crystal display element. Specifically, in the cameof liquid crystal display element 1R, the wavelength region of theemitted light of organic electroluminescent element 12 is set to red. Asin the case of liquid crystal display element 1G, the wavelength regionof the emitted light of organic electroluminescent element 12 is met togreen. And in the came of liquid crystal display element 1B, thewavelength region of the emitted light of organic electroluminescentelement 12 is set to blue.

Specifically, the distance between dielectric mirror layer 121 andreflecting electrode layer 126 in adjusted after selecting the materialof luminescent layer 125 of organic electroluminescent element 12.Although, if polarisation conversion element 13 of embodiment 4 orpolarization conversion element 14 of embodiment 5 it employed, apolarization conversion element could be employed having a polarizationselective reflection function over the entire visible light region, useof a polarization conversion element having a polarization selectivereflection function for a specific wavelength region only enables theefficiency of utilization of light to be improved.

Also, if a microlens array element (15, 17) in employed, the lens isdesigned such as to reduce aberration when light of that colour isinput. Furthermore, the reflection preventing film (152, 172) of themicrolens element is adjusted such that its reflectivity is lowest whenlight of that colour is input. For example, adjustment is effected so asto satisfy the aforementioned condition in respect of light ofwavelength 610 nm in the came of liquid crystal display element 1R, inrespect of light of wavelength 535 nm in the case of liquid crystaldisplay element 1G, and with respect to light of wavelength 470 nm inthe case of liquid crystal display element 1B.

Wavelength films 70 are constructed using a glass plate or plasticsplate. Red wavelength film 70R is constructed so as to be capable oftransmitting light of red wavelength. Green wavelength film 70G isconstructed so as to be capable of transmitting light of greenwavelength. Blue wavelength film 708 is constructed so as to be capableof transmitting light of blue wavelength. Wavelength films 70R, 70G and708 can be removed from the structural elements. Dichroic prism 60 isconstructed to be capable of combining the images from liquid crystaldisplay elements 1R, 1G and 1B. In more detail, dichroic prism 60 isconstituted by assembling a plurality of prisms, formed with dielectricmulti-layer films that reflect light of a specific wavelength at theirboundary faces. For example, film 60R is constituted to reflect light ofred wavelength and to transmit light of other wavelength. Film 603 isconstituted to reflect light of blue wavelength and to transmit light ofother wavelengths.

Projection lens 32 is adjusted to be capable of projecting a combinedimage from dichroic prism 60 on to screen 51. While only one lens isshown in the Figure, it could be constructed of a plurality of lenses.

Frame 42 is constructed with a volume capable of containing all theoptical elements of this embodiment.

Screen 51 is the same as that described with reference to embodiment 9.

(Action)

The images that are supplied from liquid crystal display elements 1R, 1Gand 1B through wavelength films 70R, 70G and 70B to dichroic prism 60are images of light of the respective primary colours. The red light isreflected by film 60R of dichroic prism 60. The blue light is reflectedby film 60B of dichroic prism 60. The green light is reflected byneither film 60R nor 60B and passes through both films. As a result, animage obtained by combination of the light of these three colours isemitted on the projection lens 32 side of dichroic prism 60. This imagein magnified and projected on to screen 51 by projection lens 32. Theimage projected on to screen 51 can be observed by an observer from therear side. For example, if the transparent liquid crystal panel isconstituted with a diagonal size of about 63.5 mm (2.5 inches), rearprojection screen 51 is formed with a diagonal size of about 1 m (about40 inches).

As described above, with this embodiment 10, liquid crystal displayelements according to the present invention are provided for eachprimary colour and these are combined to produce a colour image, so,compared with the case where illumination is effected with a singleorganic electroluminescent element emitting white light, a brightercolour image can be displayed.

Embodiment 11

Embodiment 11 of the present invention provides a construction of aliquid-crystal projection device for colour display different fromembodiment 10.

(Construction)

As shown in FIG. 14, a liquid-crystal projection device according tothis embodiment has practically the same construction as theliquid-crystal projection device of embodiment 10. However, theliquid-crystal projection device of this embodiment is further providedwith a reflecting mirror 80. It also differs from embodiment 10 in thatthere is provided a screen 52 in place of screen 51 of embodiment 10,and this is stored in frame 43. Reflecting mirror 80 is constructed soas to be capable of reflecting light from projection lens 32 in adirection at right angles with respect to the optic axis.

Screen 52 in constructed so as to be capable of projecting the imagereflected by reflecting mirror 80 such that it can be observed from theback face.

Frame 43 is constructed so as to be capable of arranging the variousoptical elements such that an image of suitable size can be formed onscreen 52.

(Action)

This is the same as in the case of embodiment 10 as far as the emissionfrom projection lens 32 of a combined image obtained by combining imagesof the respective primary colours. This combined image is reflected byreflecting mirror 80 and is projected on to screen 52. In order toproject an image of the same magnification as in embodiment 10, thedistance on the optic axis from projection lens 32 to screen 52 can bemade equal to the distance from projection lens 32 to screen 51 inembodiment 10.

With this embodiment 11, liquid crystal display elements according tothe present invention are provided for each primary colour and these arecombined to generate a colour image, so a bright colour image can bedisplayed.

Also, there is the advantage that, if a convex-surfaced mirror inprovided am the reflecting mirror, the image is further magnified bythis reflection, so large image magnification can be obtained even ifthe distance on the optic axis is short.

Also, since the image produced by reflection by the reflecting mirrorcan be inverted, if the image that in emitted from the projection lenswas inverted, this further inversion of the image enables it to becorrected to a non-inverted image.

Embodiment 12

Embodiment 12 of the present invention provides a liquid-crystalprojection device for colour display different from that of embodiment10.

(Construction)

As shown in FIG. 15, the construction of a liquid-crystal projectiondevice according to this embodiment is practically the same as that of aliquid-crystal projection device according to embodiment 10. However, aliquid-crystal projection device according to this embodiment differsfrom embodiment 10 in that, instead of a screen being incorporatedwithin the frame as in embodiment 10, an external screen 50 in arrangedto be capable of being projected on to. Projection lens 34 is arrangedto be capable of projecting a combined image on to external screen 50.In this Figure, it is constituted by a single projection lens, but anassembly of a plurality of lenses could be used. In particular, thedistance with respect to the screen for projection on to an externalscreen is not fixed. It is therefore constructed so as to focus atwhatever distance screen 50 is arranged.

Since frame 44 does not contain a screen within the frame, it isconstructed so as to be able to contain liquid crystal display element1, wavelength film 70, dichroic prism 60 and projection lens 34.

(Action)

In this embodiment, light that is emitted from projection lens 34 isprojected on to a screen arranged outside. The magnification factor ofthe image varies depending on the construction of the lens of projectionlens 34 and the distance between projection lens 34 and screen 50.

As described above, with this embodiment 12, a liquid-crystal projectiondevice can be provided which does not incorporate a screen.

Other Embodiments

It should be noted that, although, in the present embodiments, a flatplate-shaped transparent liquid crystal panel was employed, so theorganic electroluminescent elements were also made in the form of a flatplate so as to illuminate this liquid crystal panel evenly, if thedisplay surface of the liquid crystal panel were for example curved, theorganic electroluminescent elements could also be deformed so as tomatch the surface shape of the liquid crystal panel.

Also, so long as the front-side microlens array element, rear-sidemicrolens array element, polarization conversion element and transparentliquid crystal panel can provide the functions sot out in theembodiments, other constructions of these could be employed.

INDUSTRIAL APPLICABILITY

Since, with the present invention, a flat plate-shaped organicelectroluminescent element is employed whereby a larger amount of lightcan be obtained with lower drive voltage than with the conventionallight source using inorganic material, a liquid-crystal projectiondevice of small size can be provided whereby a brighter image thanconventionally can be projected.

Also, according to the present invention, if an organicelectroluminescent element is employed having a resonator structure thatemits light with better directionality of the emitted light thanconventionally to the liquid crystal panel, diminution of the quantityof light due to divergence of the light can be prevented, making Itpossible to provide a liquid-crystal projection device of small size andthat can be driven with low voltage and whereby a bright image can beprojected.

Since, according to the present invention, a polarization conversionelement is employed that can convert the polarization condition ofemitted light, a liquid-crystal projection device whereby a bright imagecan be projected can be provided, by increasing the amount of light thatcan pass through the polarizing plate of the liquid crystal panel.

According to the present invention, since, in projection of a colourimage, a polarization conversion element is employed that functions in aspecified wavelength band, the amount of light that can pass through thepolarizing plate of the liquid crystal panel is increased, enabling aliquid-crystal projection device of small size to be provided whereby abright image can be projected.

Use of a microlens array element whereby light is focused on to thepixel apertures of the liquid crystal panel according to the presentinvention increases the amount of light that can pass through the pixelapertures, thereby enabling a liquid-crystal projection device of smallsize to be provided whereby a bright image can be projected.

In the projection of a colour image according to the present invention,use of a small luminescent element whereby, due to optical resonance,only light of specific wavelength is emitted increases the amount oflight of specific wavelength thereby enabling a liquid-crystalprojection device of small size to be provided whereby a bright imagecan be projected.

What is claimed is:
 1. A liquid-crystal projection device having aliquid crystal display element, comprising: a liquid crystal panelhaving a polarization plate; an organic electroluminescent elementhaving an organic thin-film layer containing organic molecules that emita light disposed between a reflecting electrode layer that reflects thelight and a transparent electrode layer that transmits the light,wherein a half-mirror layer is provided on an optical output side of thetransparent electrode layer, the half-mirror layer reflecting a firstportion of the emitted light back through the transparent electrodelayer into the reflecting electrode layer, while transmitting a secondportion of the emitted light, a distance between the half-mirror layerand the reflecting electrode layer being set to an optical distance thatproduces a resonance of the emitted light; a transparent liquid crystalpanel that controls transmission of light emitted from) a face of theorganic electroluminescent element; and a polarization conversionelement disposed between the organic electroluminescent element and thetransparent liquid crystal panel, the polarization conversion elementconverting a polarization of emitted light from the organicelectroluminescent element, and the transparent liquid crystal panelincluding a polarizing plate that transmits light of a specifiedpolarization, of the light emitted after passing through thepolarization conversion element, a direction of polarization of light,provided through the polarization conversion element to the liquidcrystal panel, being substantially consistent with a permeable directionof polarization of light in the polarizing plate of the liquid crystalpanel.
 2. The liquid-crystal projection device according to claim 1, theorganic thin-film layer comprising a white luminescent layer that emitswhite light.
 3. The liquid-crystal projection device according to claim1, the organic thin-film layer comprising successively stacked primarycolor luminescent layers that respectively emit light of respectivewavelength regions of a plurality of primary colors necessary for colordisplay.
 4. The liquid-crystal projection device according to claim 1,the organic electroluminescent element comprising a transparentelectrode layer overlying a transparent substrate, the organic thin-filmlayer overlying the transparent electrode layer and an electrode layeroverlying the organic thin-film layer, the electrode layer reflectinglight emitted by the organic thin-film layer.
 5. The liquid-crystalprojection device according to claim 1, the polarization conversionelement comprising: a circular polarization selective reflection filterarranged on an organic electroluminescent element side and that reflectsone circularly polarized component of right-handed circularly polarizedlight and left-handed circularly polarized light and that transmitsother circularly polarized components; and a ¼ wavelength plate thatconverts circularly polarized light to linearly polarized light and thatconverts linearly polarized light to circularly polarized light.
 6. Theliquid-crystal projection device according to claim 1, the polarizationconversion element comprising: a linearly polarized light selectivereflection filter arranged on a transparent liquid crystal panel sideand that, of two perpendicular linearly polarized components, reflectsone linearly polarized component and transmits the other linearlypolarized component; and a ¼ wavelength plate that converts circularlypolarized light into linearly polarized light and that converts linearlypolarized light into circularly polarized light.
 7. The liquid-crystalprojection device according to claim 1, the polarization conversionelement comprising a polarization selective reflection filter that, forthe emitted light of a specified wavelength region, transmits light of aspecified polarization and reflects light of other polarizations.
 8. Theliquid-crystal projection device according to claim 1, furthercomprising a front-side microlens array element disposed between theorganic electroluminescent element and the transparent liquid crystalpanel, the front-side microlens array element including microlenselements that collect output light from the organic electroluminescentelement and are arranged corresponding to individual pixels of thetransparent liquid crystal panel.
 9. The liquid-crystal projectiondevice according to claim 8, a focal length of the microlens elementsand a distance between the front-side microlens array element and theliquid crystal panel being such that apertures of the individual pixelsof the transparent liquid crystal panel are arranged in a vicinity of arear-side focal point of the microlens elements.
 10. The liquid-crystalprojection device according to claim 8, the transparent liquid crystalpanel comprising an optical screening element that transmits light thatis incident on an aperture of each pixel and that screens light that isincident on portions other than the aperture of each pixel.
 11. Theliquid-crystal projection device according to claim 8, furthercomprising a rear-side microlens array element including microlenselements arranged corresponding to individual pixels, the microlenselements suppressing divergence of light transmitted through pixelapertures of the liquid crystal panel.
 12. The liquid-crystal projectiondevice according to claim 11, a focal length of a microlens elements anda distance between the rear-side microlens array element and thetransparent liquid crystal panel being such that the apertures of thepixels are arranged in a vicinity of a front-side focal point of therear-side microlens elements.
 13. The liquid-crystal projection deviceaccording to claim 8, further comprising a polarization conversionelement provided between the organic electroluminescent element and thefront-side microlens array element, the polarization conversion elementconverting a polarization of light that is output from the organicelectroluminescent element, and the transparent liquid crystal panelcomprising a polarizing plate that transmits light of a specifiedpolarization, of the light that is output after passing through thepolarization conversion element.
 14. The liquid-crystal projectiondevice according to claim 13, the polarization conversion elementcomprising: a circular polarization selective reflection filter arrangedon an organic electroluminescent element side, the polarizationconversion element reflecting one circularly polarized component ofright-handed circularly polarized light and left-handed circularlypolarized light and transmitting another circularly polarized component;and a ¼ wavelength plate that converts circularly polarized light intolinearly polarized light and that converts linearly polarized light intocircularly polarized light.
 15. The liquid-crystal projection deviceaccording to claim 13, the polarization conversion element comprising: alinear polarization selective reflection filter arranged on a front-sidemicrolens array element side, the polarization conversion elementreflecting one linearly polarized component of light and transmittinganother linearly polarized component; and a ¼ wavelength plate thatconverts circularly polarized light into linearly polarized light andthat converts linearly polarized light into circularly polarized light.16. The liquid-crystal projection device according to claim 1, furthercomprising a projection lens that projects on to a screen an imagegenerated by passing through the transparent liquid crystal panel. 17.The liquid-crystal projection device according to claim 16, furthercomprising a transparent screen, an image projected from the projectionlens being visible on a side of the transparent screen opposite from theprojection lens.
 18. The liquid-crystal projection device according toclaim 1, further comprising: a plurality of liquid crystal displayelements that control transmission of light of respective wavelengthregions of a plurality of primary colors necessary for color display; acombining optical system that generates a color image by combiningimages of primary colors emitted from the plurality of liquid crystaldisplay elements; and a projection lens that projects on to a screen acolor image combined by the combining optical system.
 19. Theliquid-crystal projection device according to claim 18, the plurality oforganic electroluminescent elements having an optical resonantstructure.
 20. The liquid-crystal projection device according to claim18, further comprising a transparent screen, an image projected from theprojection lens being visible on a side of the transparent screenopposite from the projection lens.
 21. The liquid-crystal projectiondevice according to claim 18, the liquid crystal display elementsfurther comprising a front-side microlens array between the organicelectroluminescent element and the transparent liquid crystal panel, thefront-side microlens array including microlens elements corresponding toindividual pixels of the transparent liquid crystal panel, the microlenselements collecting light emitted from the organic electroluminescentelement.
 22. The liquid-crystal projection device according to claim 21,the liquid crystal display elements further comprising a rear-sidemicrolens array element including microlens elements corresponding toeach pixel the microlens elements suppressing divergence of lightpassing through the pixel apertures of the liquid crystal panel on anoutput side of light that has passed through the transparent liquidcrystal panel.
 23. The liquid-crystal projection device according toclaim 22, the front-side microlens array element and the rear-sidemicrolens array element of the liquid crystal display elementscomprising a reflection preventing film having a lowest reflectivity forlight of the wavelength region of the primary color allocated to each ofthe liquid crystal display elements.
 24. A liquid-crystal projectiondevice, comprising, for each primary color, a liquid crystal displayelement including organic electroluminescent elements each having anorganic thin-film layer containing organic molecules that emit light, soas to be provided with an optical resonant structure adjusted such as toemit light of respective wavelength regions of the primary colorsnecessary for color display and a transparent liquid crystal panel thatcontrols transmission of light emitted from faces of the organicelectroluminescent elements; and a polarization conversion elementdisposed between the organic electroluminescent element and thetransparent liquid crystal panel, the polarization conversion elementconverting a polarisation of emitted light from the organicelectroluminescent element, and the transparent liquid crystal panelincluding a polarizing plate that transmits light of a specifiedpolarization, of the light emitted after passing through thepolarization conversion element, a direction of polarization of light,provided through the polarization conversion element to the liquidcrystal panel, being substantially consistent with a permeable directionof polarization of light in the polarizing plate of the liquid crystalpanel, the liquid crystal projection device further comprising: acombining optical system that generates a color image by combiningimages of each primary color emitted from respective liquid crystaldisplay elements, and a projection lens that projects on to a screen thecolor image combined by the combining optical system.
 25. Theliquid-crystal projection device according to claim 24, the liquidcrystal display elements, between the organic electroluminescentelements and the front-side microlens array element, further comprisinga polarization conversion element that converts a polarization ofemitted light from the organic electroluminescent element, and thetransparent liquid crystal panel including a polarizing plate thattransmits light of a specified polarization of light that is emittedafter having passed through the polarization conversion element.
 26. Theliquid-crystal projection device according to claim 25, the polarizationconversion element of the liquid crystal display elements comprising apolarization selective reflection filter that transmits light of aspecified polarization with respect to the emitted light of a specifiedwavelength region and that reflects light of other polarizations.
 27. Aliquid-crystal display element, comprising: an organicelectroluminescent element having an organic thin-film layer containingorganic molecules that emit light disposed between an electrode layerthat reflects light and an electrode layer that transmits light; atransparent liquid crystal panel that controls transmission of lightemitted from a face of the organic electroluminescent element; and apolarization conversion element disposed between the organicelectroluminescent element and the transparent liquid crystal panel, thepolarization conversion element converting a polarization of emittedlight from the organic electroluminescent element, and the transparentliquid crystal panel including a polarizing plate that transmits lightof a specified polarization, of the light emitted after passing throughthe polarization conversion elements, a direction of polarisation oflight, provided through the polarization conversion element to theliquid crystal panel, being substantially consistent with a permeabledirection of polarization of light in the polarizing plate of the liquidcrystal panel.
 28. The liquid-crystal display element according to claim27, wherein the polarization conversion element transmits a firstportion of the emitted light of a desired polarization and reflects asecond portion of the emitted light of a non-desired polarization.